ROTORUA DRAINAGE.

New Zealand Herald, Volume LXIX, Issue 21201, 6 June 1932, Page 9

ROTORUA DRAINAGE.

WHAKAREWAREWA SCHEME,

UNIQUE TASK PRESENTED.

Some time ago the Rotorua Borough Council decided to instal .an up-to-data sewerage system at Whakarewarewa native village, and at a meeting of the council last week notice of intention to consider the raising of a loan of £3IOO for carrying out the work was given. Owing to the thermal activity and uni certain nature of the subsoil foundation the execution of the work will present many very difficult problems, and is a task unique in the drainage engineering history of New Zealand. v In reporting upon the proposed schema the drainage engineer, Mr. F. J. .-ffenilian, said that in the pa area, where , a good deal of thermal country would be traversed, excavation would be carried out to an absolute minimum depth. To ensure that no serious thermal resistance* would be met with, approximately 800 ground tests had been made on the routes of tho mains. On no account would excavations for any purposes bo carried out unless the ground had been tested well below the required levels. In localities where abnormal ground temperatures existed pipe joints would bo made of a mixture of sulphur and sand. All other pipe jointing would ba carried out with Petrolastic asphalt. Glazed earthenware pipes would be used throughout. Generally, tho country was solid and unyielding, but if foundations were required they would bo constructed of sulphur grouted flat spawls finished off to required level with consolidated spoil. Where the ground was affected with sulphur, manholes and chambers would ba constructed of brick. The bricks would be cement-jointed, after which the joints' would bo raked out and overfilled with a mixture of bitumen and sand. All surfaces would then be coated with a bituminous paint. Manholes and chambers would bo built on a 6in. layer of bitumen concrete. All benching would consist of bitumen concrete finished with a coat of bitumen plaster. 1